JPH04232925A - Electrochromic window - Google Patents

Abstract

PURPOSE: To improve an electrochromic reaction rate by forming a solid high- polymer electrolyte disposed between specific electrodes of a solid soln. of an ionic lithium compd. in a specific solid crosslinked polyepoxide. CONSTITUTION: A glass supporting body 1 has a layer 2 of the oxide of tin and indium and, further, a tungsten oxide layer 3 is precipitated thereon. The solid high-polymer electrolyte 4 consist of the film-like solid crosslinked polyepoxide contg. lithium perchlorate. This crosslinked polyepoxide is a product which is obtd. by copolymerizing the epoxide expressed by formula II and the monoepoxide expressed by formula I at a mutual molar ratio of 2:100 and has a weight average mol.wt. of about 25000AMU and a glass transition temp. of -77 deg.C. In the formula I, R is a methyl group or ethyl group and (n) is an integer from 1 to 6. In the formula II, (m) is an integer from 1 to 6.

Description

[Detailed description of the invention]

The present invention relates to electrochromic windows (with improved properties) based on the use of polymeric polyepoxide electrolytes.

Optical devices are known in the art that can be switched from a maximum transmission state to an opposite minimum transmission state when an electrical signal is applied. These devices have received considerable attention in the architectural and automotive fields for their energy savings. In these devices, optical modulation is preferably induced by electrochemical methods through the use of electrochromic substances. "Electrochromic material" refers to a compound that can undergo a reversible change in hue upon suitable electrochemical treatment. A typical example is tungsten oxide (W
O3), and the compound changes from transparent to blue by an electrochemical intercalation method as described below. This occurs within a cell containing a transparent electrolyte that supplies the intercalating ions M+ (usually alkali metal ions). The cell is made of an otherwise optically immobile material (i.e., a material that is transparent regardless of whether the applied signal is an anode signal or a cathode signal), or a WO
If it contains an electrochromic material with complementary properties to 3, it will be dark (due to the formation of blue MxWO3) when a signal (e.g. cathodic signal) is applied, while the opposite signal (e.g. anodic signal) A device is obtained which returns to transparency (by reverting to light colored WO3) when . Thus, by applying a square wave signal, the light transmission of the device can be modulated, thereby giving the device the properties of an electrochromic window, which has important technical significance as described above. Regarding this known technique, B. See Chimicaoggi, June 1989, pp. 41-45.

[0003] In the technical field to which the present invention relates, in order to achieve a rapid and reversible electrochromic reaction, both the stacked form of a solid electrochromic device and the electrochromic material have been developed. There are demands for improvement. The patent application filed by the same applicant has a laminated structure between a tungsten oxide layer and a nickel oxide layer (these layers are on a glass support made electrically conductive by a film of indium and tin oxides). An electrochromic window is disclosed that is endowed with improved performance through the use of a solid polyelectrolyte based on a cross-linked polyether intercalated with the deposited polyether.

[0004] The inventors have discovered that by employing a polyepoxy-based solid polymer electrolyte in an electrochromic window, its performance, particularly regarding the rate of electrochromic reaction, can be further improved. This led to the present invention. According to this, the present invention provides (a) a tungsten oxide (WO3) electrode provided on a transparent conductive glass plate having a conductive material layer of tin oxide or tin and indium oxide on the inner surface; b) Nickel oxide (NiOz) activated by electrochemical intercalation of metallic lithium on a transparent conductive glass plate with a conductive material layer of tin oxide or oxides of tin and indium on the inner surface; Here z is 1 or 1
．． 66), and (c) a solid polymer electrolyte disposed between the electrode (a) and the counter electrode (b), the polymer electrolyte having the general formula ( I) (wherein R is a methyl group or an ethyl group, and n is an integer of 1 to 6);
I) (wherein m is an integer of 1 to 6) diepoxide (II): monoepoxide (
A weight average molecular weight of at least 10,000 A obtained by copolymerizing I) in a molar ratio of 1:100 to 10:100.
MU and glass transition temperature (Tg) -60 to -80
The present invention relates to an electrochromic window characterized in that it is formed of a solid solution of an ionic lithium compound in a solid crosslinked polyepoxide having a temperature of .degree.

In the electrochromic window according to the invention, tungsten oxide electrodes are deposited on glass plates made conductive by tin oxide or tin and indium oxide films by sputtering or evaporation methods according to techniques currently known in the art. Tungsten oxide (WO3
) is prepared by depositing a thin layer of The tungsten oxide layer is typically about 3000 Å thick. The conductive glass is a commercially available product. A nickel oxide counter electrode is also prepared by deposition onto conductive glass according to methods known in the art. However, in this early phase, nickel oxide cannot act as a counter electrode in the electrochromic window. Therefore, activation treatment by lithium pre-intercalation is required. For this purpose, the electrode is inserted into a cell containing a solution containing a lithium salt (eg lithium perchlorate) in an aprotic solvent (eg propylene carbonate) and a metallic lithium counter electrode. Cathode polarization causes intercalation of lithium within the nickel oxide. This treatment changes the optical properties of the nickel oxide layer. In fact, due to the lithium that has penetrated into its structure, the nickel oxide becomes transparent and can be reversibly loaded with said lithium without losing its transparency or returning to its colored state by an electrochromic reaction complementary to that of WO3. Or you can get it back. In the electrochromic window according to the invention,
A solid polymer electrolyte located between the electrode (a) and the counter electrode (b) is constituted by a solid solution of an ionic lithium compound in a solid crosslinked polyepoxide. The ionic compound of lithium is advantageously lithium perchlorate,
selected from lithium borate, lithium fluoroborate, lithium thiocyanate, lithium hexafluoroarsenate, lithium trifluoroacetate, and lithium trifluoromethanesulfonate. Among these, lithium perchlorate is preferred. The solid crosslinked polyepoxide useful for the purpose of the present invention is preferably a diepoxide (II) and a monoepoxide (I) in which R in the general formula is a methyl group and n and m are integers of 1 to 6. Molar ratio 1:1
Weight average molecular weight 10,000 to 100,000 A obtained by copolymerizing at a ratio of 00 to 6:100
The product has MU. The atomic ratio of oxygen in the polyepoxide to lithium in the ionic compound in the solid polymer electrolyte is in the range of 6:1 to 24:1,
Preferably the ratio is about 14:1.

FIG. 1 shows a preferred example of a window according to the present invention. In particular, in this figure, reference numeral 1 designates a glass support, which has a layer 2 of tin and indium oxides, on which a tungsten oxide layer (about 3000 Å thick) 3 is deposited by sputtering. has been done. Reference numeral 4 indicates a solid polymer electrolyte. This electrolyte is in the form of a film about 100 μm thick and is made of solid crosslinked polyepoxide containing lithium perchlorate. More specifically, this crosslinked polyepoxide is obtained by copolymerizing diepoxide represented by the formula and monoepoxide represented by the formula at a mutual molar ratio of 2:100 and has a weight average molecular weight of about
5000 AMU (Atomic Mass Unit)
s) and a glass transition temperature (Tg) of -77°C. Lithium perchlorate is dissolved in the polyepoxide in an amount such that the atomic ratio of oxygen (contained in the polyepoxide) to lithium (contained in the lithium perchlorate) is about 14:1. Reference numeral 5 indicates a glass support. The support has a layer 6 of oxides of tin and indium;
On this layer, a layer 7 of nickel oxide activated via intercalation with lithium is deposited by operating as described above. Reference numeral 8 indicates a sealant. 9 is a spacer, 10 is an external generator of square wave voltage, and 11 is a line connecting the voltage source 10 with two terminals connecting the conductive layer of the electrode and the conductive layer of the counter electrode. The electrochromic window shown in FIG. 1 is operated with a square wave signal that generally varies within the range of -2 volts to +2 volts. During the negative impulse (cathode WO3) the window is dark (WO
During the subsequent positive impulse (anode WO3), the window changes from dark to transparent (deintercalation of lithium from WO3) and the transmittance is large. This behavior (repeated very many times) is relevant for the following reaction. This behavior is schematically illustrated in FIG. The time required for the electrochromic reaction (ie, cathodic and anodic reactions) to complete is approximately tens of seconds. This time varies depending on the value of the signal activating the cell. For a +2.5 volt to -3 volt square wave, the change in transmission from minimum to maximum and vice versa is achieved within a time of about 20 seconds.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a preferred embodiment of an electrochromic window according to the present invention.

FIG. 2 is a graph showing the behavior of the electrochromic window of the present invention.

[Explanation of symbols]

1,5 Glass support 2,6 Tin and indium oxide layer 3
Electrode 4 Solid polymer electrolyte 7 Counter electrode 8 Sealant 9 Spacer 10 Voltage source 11 Line

Claims (8)

[Claims] 1. (a) a tungsten oxide (WO3) electrode provided on a transparent conductive glass plate having a conductive material layer of tin oxide or tin and indium oxide on the inner surface;
(b) Nickel oxide (NiOz ;here z
is 1 to 1.66), and (c) a solid polymer electrolyte disposed between the electrode (a) and the counter electrode (b), the polymer electrolyte , a monoepoxide represented by the general formula (I) (wherein R is a methyl group or an ethyl group, and n is an integer of 1 to 6), and a monoepoxide represented by the general formula (II) (wherein, m is is an integer from 1 to 6) and diepoxide (II):monoepoxide (
A weight average molecular weight of at least 10,000 A obtained by copolymerizing I) in a molar ratio of 1:100 to 10:100.
MU and glass transition temperature (Tg) -60 to -80
characterized by being formed of a solid solution of an ionic lithium compound in a solid crosslinked polyepoxide having a temperature of
electrochromic window. 2. The tungsten oxide electrode according to claim 1, wherein the tungsten oxide electrode is obtained by depositing a tungsten oxide layer with a thickness of about 3000 Å on a conductive glass by sputtering or evaporation. electrochromic window. 3. The nickel oxide counter electrode according to claim 1, wherein the nickel oxide counter electrode is obtained by depositing nickel oxide on conductive glass and then activating it by electrochemical intercalation of lithium. An electrochromic window. 4. The product according to claim 1, wherein the ionic lithium compound is lithium perchlorate, lithium borate, lithium fluoroborate, lithium thiocyanate,
An electrochromic window selected from lithium hexafluoroarsenate, lithium trifluoroacetate and lithium trifluoromethanesulfonate. 5. The electrochromic window of claim 4, wherein the ionic lithium compound is lithium perchlorate. 6. The solid crosslinked polyepoxide according to claim 1, wherein R in the general formula is a methyl group, and n and m are integers of 1 to 6, diepoxide (II) and monoepoxide ( I) in mutual molar ratio 1:
Weight average molecular weight 10,000 to 100,000 obtained by copolymerizing at a ratio of 100 to 6:100
Electrochromic windows, products with AMU. 7. The product according to claim 1, wherein the atomic ratio of oxygen in the polyepoxide to lithium in the ionic compound in the solid polymer electrolyte is 6:1 to 2.
Electrochromic window that is 4:1, preferably 14:1. 8. The method of claim 1 further comprising a square wave voltage source and a line connecting said voltage source to two terminals respectively connected to the conductive material layers of said electrode and counter electrode. electrochromic window.